• Corrosion Science and Technology
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• v.19 no.3
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• pp.109-114
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• 2020

The photo-reflectance of aluminum and AISI 304 stainless steel during cyclic immersion test in 3 wt% NaCl solution was examined in this study. Overall, corrosion was not recognized by a visual inspection or weight measurement up to 310 h. When evaluated, it was noted that the roughness of the specimens did not change significantly. However, localized corrosion, which is located at the vicinity of intermetallic precipitation of aluminum or at the grain boundary of stainless steel, was confirmed by the use of an optical microscope and scanning electron microscopy after tens of hours of utilizing the corrosion test. In this respect, an increase of the peak intensity for metallic Al after 90 h of test, and for metallic Fe after 153 h was detected from the X-ray photoelectron spectra. In this context, it was shown that from the photo-reflectance spectra, the reflection of the visible light from the tested samples was changed noticeably over the test duration. As a result, the intensity of reflected light was decreased up to 90 h ~ 153 h, and thereafter was shown to increase higher than the initial intensity before the corrosion test.

• The Journal of the Korea Contents Association
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• v.21 no.2
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• pp.707-717
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• 2021

The purpose of this study was to explore whether PPAT drawing using an application can be developed on digital devices for game addicts. The PPAT drawing test is useful and reliable for verifying problem-solving skills in how people pick apples. As a result of this study, the over-immersion group scored lower than the average user group in the "problem Solving" category of the PPAT drawing test using the PPAT drawing applicaion on digital devices, and expressed by not reaching for apples, or by picking apples without reasonable support. The findings in this study suggest that the PPAT drawing test application on digital devices has significantly demonstrated its original purpose of 'problem resolution', as well as future psychotherapeutic interventions for Internet over-immersion subjects as well as users who are familiar with digital devices.

• Development and Reproduction
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• v.15 no.4
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• pp.301-308
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• 2011

The tolerance evaluation for abalone Haliotis discus hannai embryos was performed using different concentrations of cryoprotective agents (CPAs): dimethyl sulfoxide, ethylene glycol and propylene glycol added to 0.2 M sucrose, respectively. 4-cell, trochophore and veliger were exposed in each CPA with different concentration for 10, 20 and 30 minutes of immersion time. Developmental rates were increased with decreased concentration of every CPA and decreased immersion time, and differed from types of CPA. Developmental rates of veliger in all the CPAs were higher than those of 4-cell and trochophore. The developmental rates and larval activity indices in ethylene glycol were comparatively higher than those in other CPAs and the effective CPA and its concentration for the cryopreservation of the abalone embryos was suggested as 2.0 M ethylene glycol with equilibration time of 30 minutes.

• Human Ecology Research
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• v.58 no.4
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• pp.585-599
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• 2020

This study investigated children's interests in learning English, affected by educational activities in and out of institutes, and mothers' perceptions regarding early childhood English education. We recruited, 253 mothers of 3- to 5-year-old children in either general kindergartens or English immersion institutes. They answered questions on socioeconomic status, perceived interest in English by their children, their perceptions regarding early childhood English education, and English education outside institutes. In addition, 42 English teachers provided information within institutes such as class time per week, teacher-pupil rate, and language use policy during class. The collected data were analyzed through SPSS 22 for frequency analysis, descriptive statistics, independent t-test, and hierarchical multiple regression analysis. The major findings are as follows. First, the two groups were in distinct learning environment. Second, mothers' perceptions and outside-institute activities were significantly different between the two groups. Third, the English interests of children at both institutes were influenced by mothers' worries and at-home English interactions. Fourth, education within institutes did not affect both group's English interests. Fifth, private education and socioeconomic status did not affect both group's English interests. Lastly, only the children's interests in English immersion institutes were affected by gender and mother's perceived necessities. Focusing children's interests, this study helps in understanding young children's affective aspects regarding learning English. The findings are expected to be a guideline for each home and institute to increase children's interest in learning English.

• Journal of the Korean Society for Nondestructive Testing
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• v.24 no.4
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• pp.348-353
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• 2004

This study is aimed for the implementation of ultrasonic method to assess the reliability of turbine bearings. A modified ultrasonic immersion technique was carried out in both laboratory experiment and field application. From the laboratory results, we confirmed that the condition of interface layer between the babbitt and base metal be monitored by the C-Scan. The C-scan image by the ultrasonic immersion test can be used successfully to observe the condition of interface layer. The testing with a focused transducer provides a promising approach for estimating the extent of the damaged region and observing the interface layer effectively. The difference of the ultrasonic reflection ratio between the bonding and debonding area at the interface layer is one of the key parameters for assessing the extent of the damaged area; additionally, the reflection amplitude exhibits a favorable correlation with the overall damage level. The technique developed in this study was applied to the inspection of the turbine bearings at several power plants in Korea whereby the applicability in the field can be ascertained.

• Korean Journal of Metals and Materials
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• v.50 no.9
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• pp.697-702
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• 2012

In this study, unidirectional and plain woven carbon fiber reinforced magnesium matrix composite laminates were fabricated by the liquid pressing infiltration process, and evolutions of the microstructure and compressive strength of the composite laminates under corrosion were investigated by static immersion tests. In the case of the unidirectional composite laminate, the main microstructural damage during immersion appeared as a form of corrosion induced cracks, which were formed at both CF/Mg interfaces and the interfaces between layers. On the otherhand, wrap/fill interface cracks were mainly formed in the plain woven composite laminate, without any cracks at the CF/Mg interface. The formation of these cracks was considered to be associated with internal thermal residual stress, which was generated during cooling after the fabrication process of these materials. As a consequence of the corrosion induced cracks, the thickness of both laminates increased in directions vertical to the fibers with increasing immersion time. With increasing immersion time, the compressive strengths of both composite laminates also decreased continuously. It was found that the plain woven composite laminates have superior corrosion resistance and stability under a corrosive condition than unidirectional laminates.

• The Journal of the Korea Contents Association
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• v.22 no.6
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• pp.307-318
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• 2022

Virtual reality is actively used in the medical field as a learning effectiveness that induces immersion, but research on the factors that induce learning immersion is insufficient. Therefore, this study extracted the usability and cognitive affordance evaluation elements of the interface through literature research and selected four types of virtual reality medical contents to conduct a Useability-Test for experts. Based on this, an interface design method according to virtual reality medical technology content was proposed. In summary, it can be seen that the information-providing interface affects immersion due to visibility, distance from the experience's gaze, color harmony, uniform visualization, feedback, reaction speed, and expected changes resulting from manipulation, and does not impair immersion. This study has limitations in generalization using limited content, so it is expected that continuous research will discuss the development of standardized guides in interface design and the precision of interface design research from a user perspective.

• Proceedings of the Korean Nuclear Society Conference
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• 2005.10a
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• pp.995-996
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• 2005

• Journal of Ocean Engineering and Technology
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• v.30 no.4
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• pp.327-333
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• 2016

Reinforced concrete structures have found wide usage in land and maritime applications. However, the corrosion of reinforced concrete has been recognized as a serious problem from economic and safety standpoints. In previous studies, the corrosion behavior of the inner steel bar embedded in mortar (W/C: 0.4, 0.5) was investigated using electrochemical methods. In this study, multiple mortar test specimens (W/C: 0.6) with six different cover thicknesses were prepared and immersed in flowing seawater for five years. Subsequently, equations related to the cover thickness, period of immersion, and corrosion characteristics of the embedded steel bar were evaluated using electrochemical methods. Prior to immersion, the corrosion potentials indicated an increase with increasing cover thickness, and after five years, all corrosion potentials demonstrated a trend in the positive direction irrespective of the cover thickness. However, the relationships between the corrosion potential and cover thickness were not in complete agreement. Furthermore, after five years, all of the corrosion potentials indicated values that were nobler compared to those obtained prior to immersion, and their corrosion current densities also decreased compared to their values obtained prior to immersion. It was considered that the embedded steel bar was easily corroded because of the aggression of water, dissolved oxygen, and chloride ions; a higher W/C ratio also assisted the corrosion process. The corrosive products deposited on the surface of the steel bar for five years cast a resistance polarizing effect shifting the corrosion potential in the nobler direction. Consequently, it was considered that the W/C ratio of 0.6 showed nearly same results as those of W/C of 0.4 and 0.5. Therefore, the corrosion potential as well as various parameters such as the cover thickness, period of immersion, and W/C ratio must be considered at once for a more accurate evaluation of the corrosion property of reinforced steel exposed to marine environment for a long period.

• Journal of the Korean institute of surface engineering
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• v.42 no.6
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• pp.280-286
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• 2009

In this study, the corrosion property of copper alloy tubes in seawater has been investigated. Three copper alloys of nominal composition Cu-20Zn-2Al(Al-Brass), Cu-30Ni(CN70/30) and Cu-10Ni(CN90/10) were considered. The samples were immersed in 3%NaCl flowing solution at $90^{\circ}C$ for 30, 50 and 80 days. Corrosion rate of copper alloy tubes in 3%NaCl flowing solution was investigated by weight-loss measurements and electrochemical test. The CN70/30 showed lowest corrosion rate among three copper alloy tubes. Because of passive films formation, corrosion rates of three types of copper tubes were decrease with time. Surface characteristics of copper alloy tubes were analyzed by optical micrograph(OM), scanning electronic microscopy (SEM), energy dispersive X-ray analysis(EDAX) and X-ray diffraction patterns(XRD). CN70/30 showed partly pitting problem on the surface owing to high Fe content, even though having high resistant against corrosion. Cracks appeared on the surface of CN90/10 and CN70/30 after more than 50 days immersion, which could be derived from high nickel contents.